My fantasy for Roger Sterling—Mad Men’s last gasp of fifties hubris and hedonism—is that, come 1966 or so, he will drop acid, most likely at the behest of a pretty young thing, and turn into a counterculture freak like Timothy Leary. Which, as it turns out, isn’t so far-fetched. “There were rumblings about something like that happening,” says John Slattery, who has embodied Roger for what will soon be four seasons on AMC’s hit series Mad Men. Slattery would be fine with that; at the very least, he could ditch the snugly tailored suits. “It would be nice if the show runs until 1970. I would love to get into a pair of elephant bells.”

That would surely startle admirers of Roger Sterling’s easy, martini-enhanced hauteur, but it’s less surprising once you meet Slattery. As he bounds up the steps of Santa Monica’s Urth Caffé, I’m reminded of something Mad Men creator Matthew Weiner told me about directing Slattery: “I said to John early on, ‘You have to be less athletic. Roger doesn’t surf like you.'"

Slattery, 47, is SoCal casual in jeans and a T-shirt, his black-framed glasses a subtle nod to downtown New York, where he lives when he’s not shooting Mad Men. He says he was in the water at 5 a.m., the better to hang ten alone. “The whole laid-back thing in Beach Boys songs doesn’t really exist. Surfers are not a generous group,” says Slattery, who is humorous with a prickly edge (chalk it up to his Boston Irish roots). “They can get pretty unfriendly and territorial—there are only so many waves.”

Or so many clients, as the case may be. In season four of Mad Men, we find Roger Sterling, if not a new man, then a reinvigorated one. It’s November 1964, and Roger and Don Draper (Jon Hamm) are deep into running their rebel agency, Sterling Cooper Draper Pryce, with a few hand-picked employees from the old Sterling Cooper, including Roger’s former mistress, Joan Holloway (Christina Hendricks). It’s a turn of events that could promise more Roger, after a season of not nearly enough.

That he’s emerged as a sympathetic character is, on paper, absurd. Over the past three seasons, he’s misbehaved epically, getting plastered and hitting on Don’s wife, Betty; divorcing his own perfectly nice wife, Mona (played by Slattery’s wife, Talia Balsam); marrying an obvious twit; holding his daughter’s wedding the day after President Kennedy’s assassination; and, most deplorably, performing “My Old Kentucky Home” in blackface at a country club. “When I saw the Derby Day script a day before the table read, I thought, You’ve got to be kidding me,” says Slattery. “I texted Hamm—‘Would you do this?’ Like I had any choice.” Slattery laughs. “It was great, but I didn’t want to be the one to do it. Then I realized, you can’t really ride the girl in your underwear, singing cowboy songs, then refuse to do the blackface.”

Slattery jokes that he thought he would get shot. But the negative reaction turned out to be minimal. “No one said, ‘This is too much,’ because it obviously happened back then,” he says. It wasn’t historical probability that made the blackface okay, however; it was who was doing it. Credit Slattery’s rakish charm, the boyishness he suggests beneath Roger’s patrician veneer, his deadpan precision with a funny line—and he gets the show’s choicest lines. But don’t discount Weiner’s identification with and affection for Roger. "Hang around me, and you’ll hear me coming out of Peggy’s mouth, and Pete’s,” says Weiner. “But Roger does have my sense of humor, the same lack of respect for authority, the at-times-complete selfishness, and the ability to laugh at seriousness. Roger is entitled, and there’s nothing funnier than that.”

As the show’s pickled truth-sayer, Roger expresses what everyone else thinks, particularly to Don. Their relationship is Mad Men’s great unspoken love story. Women come and go, but their chemistry remains, sometimes combusting but more often producing exquisite sparks. Hamm chuckles at that but doesn’t disagree, saying that he’s pretty much Slattery’s straight man onscreen and off. “John and I do have personal chemistry,” he says. “One of the things we tried to show in season three is what happens when that’s shaken up. The reconciliation in the final episode made it one of the most rewarding of the year.” Weiner refers to Roger as Don’s id. “Roger is comfortable with his mind. Don is filled with anxiety and shame—the biggest difference between them is shame. Probably has to do with their mothers,” he adds with a laugh.

Slattery says Weiner got furious with him recently, when he ad-libbed a line. “Matt said, ‘Don’t you think I fucking thought of that? That’s why I wrote what I wrote!’" Slattery laughs. Yes, Weiner is dictatorial, but so what? “Somebody has to be,” says the actor. “I’ve worked with plenty of people who make horrible decisions.